1. Field of the Invention
The present invention relates to a sewing machine and more particularly relates to an amplitude adjusting device of a sewing machine, which is simple in structure and easy in operation which may be optionally switched between one operation mode in which a sewing machine is able to freely vary the width of stitches with manipulation of an operating knob and another operation mode in which the sewing machine user is able to determine an optional constant width of stitches only by setting the operating knob at an optional position thereof.
2. Description of the Prior Art
There have been the sewing machines provided with an amplitude adjusting device wherein an operating knob is normally urged to an initial position where a needle bar holder is set at a null amplitude, that is, not to be laterally reciprocated while a pattern cam is rotated and wherein the operating knob may be rotated in one direction from the initial position against the urging action and may be fixed at an optional angular position thereof to cause the needle bar holder to be laterally reciprocated with a constant amplitude. It is, however, very difficult to hold and maintain the operating knob at an optional fixed position against the urging action. In fact, it requires a considerably complicated mechanism which is difficult and time consuming to assemble and is, therefore, costly.